1. Field of the Invention
The present invention relates to a semiconductor device. More particularly, the present invention relates to a thin film transistor.
2. Description of Related Art
As modern information technology advances, various types of displays have been widely used in screens for consumer electronic products such as mobile phones, notebook computers, digital cameras, and personal digital assistants (PDAs). Among these displays, liquid crystal displays (LCD) and organic electroluminescence displays (OELD) are the prevailing products in the market due to their advantages of being light-weight, compact, and low in power-consumption. The manufacturing process for both LCD and OELD includes forming semiconductor devices arranged in array on a substrate and the semiconductor devices include thin film transistors (TFTs).
Conventionally, thin film transistors include top-gate TFTs and bottom-gate TFTs. These TFTs have only one semiconductor layer severing as an active layer or a channel layer. The semiconductor layer of the TFTs easily generates photo current leakage if it is irradiated with light from a front-light, a backlight or an external light. The photo current leakage causes image sticking and deteriorating the display quality of the displays.